1. Field of the Invention
This invention relates to a semiconductor integrated circuit device, and more particularly to a wiring connection structure in a lead on chip (LOC) type semiconductor integrated circuit device.
2. Description of the Related Art
Since an LOC type semiconductor integrated circuit device in which leads of a lead frame are extended on a semiconductor chip and the tip parts of the leads are connected to bonding pads by means of bonding wires enables one to increase the area of the semiconductor chip and to install the bonding pads not only in the periphery of the semiconductor chip but also in its central part, the device is in widespread use in recent years.
An example of the prior art LOC type semiconductor integrated circuit device is shown in FIG. 1. Bonding pads 13 for supplying power supply potentials (abbreviated as power supply pads hereinafter) and bonding pads 12 for supplying and receiving clock signals, address signals, data input and output signals, or the like (abbreviated as signal pads hereinafter) are disposed in the direction of the long side of the semiconductor chip 11 at its central part. It should be mentioned that in each of the drawings a black square indicates a power supply pad and an unpainted square indicates a signal pad. Leads 15 for supplying power supply potentials (abbreviated as power supply leads hereinafter) and leads 14 for supplying and receiving various kinds of signals (abbreviated as signal leads hereinafter) come onto the semiconductor chip 11 with their tip parts connected to the corresponding power supply pads 13 and signal pads 12, respectively by the bonding wires 17. However, in this type of semiconductor integrated circuit has problem which the power supply leads 15 are required corresponding to a plurality of power supply pads 13 so that the leads of the lead frame end up with a large number.
To solve this problem, if one employs a method in which a power supply wiring layer is formed on the semiconductor chip by photolithography technique and the power supply potentials provided are connected to the same plurality of power supply pads 13 by laying the wiring layer around, the number of the power supply leads 15 can be reduced. However, in this method the resistance and the parasitic capacity of the wiring layer are increased due to the elongation of the power supply wiring layer, thereby bringing about an adverse effect on the properties of the device.
As a technique for eliminating the above-mentioned inconvenience, an LOC type semiconductor integrated circuit device as shown in FIG. 2 is disclosed in U.S. Pat. No. 4,916,519. In the figure, a power supply lead structure for supplying a first power supply potential, for example, for supplying potential Vcc, is constructed by inserting a connecting conductor part 26a between a pair of power supply leads 25a and 25b to form a unified body, and another power supply lead structure for supplying a second power supply potential, for example, for supplying the ground (GND) potential, is constructed by inserting a connecting conductor part 26b between a pair of power supply leads 25c and 25d to form a unified body. The power supply pads 13 for supplying potential Vcc are connected to the connecting conductor part 26a by the bonding wires 17, and the power supply pads 13 for supplying potential GND are connected to the connecting conductor part 26b by the bonding wires 17. The signal pads 12 are connected to the corresponding signal leads 14 by means of the bonding wires 27. However, since the connecting conductor parts 26a and 26b for supplying potentials are disposed between the signal pads 12 and the signal leads 14, the bonding wires 27 grade separate the connecting conductor parts 26a and 26b , that is, cross over the connecting conductor parts 26a and 26b . However, in the above-mentioned structure there is a possibility of generating an accident in which the bonding wires 27 that straddle over the connecting conductor parts may sag down and the bonding wires 27 which form the signal system may be short circuited to the connecting conductor parts which form the power supply system.